"The mighty claws of these crabs are useful weapons to deter predators and competitors," say scientists from the Okinawa Churashima Foundation.

"In summary, coconut crabs have the ability to exert the greatest force among almost all terrestrial animals."

Coconut crabs are well adapted to life on land.

Unlike most crabs, they only return to the sea to lay their eggs.

They can also climb trees and cut coconuts down.

Despite their size and strength, little is known about coconut crabs and whether or not they are a threatened species.

'Monstrous'

Charles Darwin described the coconut crab as of "monstrous size" when he saw them on the Cocos (Keeling Islands) in the Indian Ocean during the voyage of the Beagle.

He wrote: "To show the wonderful strength of the front pair of pincers, I may mention that Captain Moresby confined one in a strong tin box, which had held biscuits, the lid being secured with wire; but the crab turned down the edges and escaped.

"In turning down the edges it actually punched many small holes quite through the tin!"